Interacción entre los recursos y el pastoreo como controles de la estructura y la dinámica de pastizales naturales

La estructura y el funcionamiento de las comunidades vegetales dependen de la disponibilidad de nutrientes para las plantas y del consumo de biomasa por los herbívoros, que generan efectos opuestos sobre la vegetación. Para comprender el resultado de la interacción entre el pastoreo y los nutrientes sobre la vegetación es necesario considerar las distintas vías que son modificadas en simultáneo por ambos controles. El objetivo general fue estudiar la interacción entre el pastoreo doméstico y la disponibilidad de nutrientes sobre la estructura, el funcionamiento y la estabilidad temporal de la vegetación de pastizales y los mecanismos involucrados en su respuesta. Se realizó un experimento factorial en el que se manipuló la presencia de ganado doméstico y la disponibilidad de nutrientes (fertilización con N, P y K + micronutrientes; n = 6 bloques) durante 5 años en un pastizal natural bajo uso ganadero (Pampa Deprimida, Argentina). La fertilización incrementó la productividad primaria neta aérea (PPNA) bajo pastoreo, lo que combinado con aumentos en la calidad de los tejidos vegetales intensificó el consumo por el ganado y redujo la biomasa vegetal en pie. En cambio, en las exclusiones al ganado la fertilización no produjo cambios, posiblemente porque el crecimiento vegetal se encontraba limitado por la luz. Los cambios de la composición vegetal debidos al pastoreo y la fertilización, principalmente incrementos de la dominancia, se relacionaron con aumentos de la biomasa aérea. Por último, el pastoreo y la diversidad de especies y grupos funcionales de plantas promovieron la estabilidad de la PPNA, mientras que los niveles intermedios de dominancia de especies la disminuyeron. Esta tesis avanzó en el conocimiento de los mecanismos que regulan la interacción entre el pastoreo doméstico y los aumentos crónicos de nutrientes sobre la estructura, funcionamiento y estabilidad de la vegetación, lo que va a permitir mejorar las estrategias de manejo y conservación de los pastizales templados

Interacción entre los recursos y el pastoreo como controles de la estructura y la dinámica de pastizales naturales

La estructura y el funcionamiento de las comunidades vegetales dependen de la disponibilidad de nutrientes para las plantas y del consumo de biomasa por los herbívoros, que generan efectos opuestos sobre la vegetación. Para comprender el resultado de la interacción entre el pastoreo y los nutrientes sobre la vegetación es necesario considerar las distintas vías que son modificadas en simultáneo por ambos controles. El objetivo general fue estudiar la interacción entre el pastoreo doméstico y la disponibilidad de nutrientes sobre la estructura, el funcionamiento y la estabilidad temporal de la vegetación de pastizales y los mecanismos involucrados en su respuesta. Se realizó un experimento factorial en el que se manipuló la presencia de ganado doméstico y la disponibilidad de nutrientes (fertilización con N, P y K + micronutrientes; n = 6 bloques) durante 5 años en un pastizal natural bajo uso ganadero (Pampa Deprimida, Argentina). La fertilización incrementó la productividad primaria neta aérea (PPNA) bajo pastoreo, lo que combinado con aumentos en la calidad de los tejidos vegetales intensificó el consumo por el ganado y redujo la biomasa vegetal en pie. En cambio, en las exclusiones al ganado la fertilización no produjo cambios, posiblemente porque el crecimiento vegetal se encontraba limitado por la luz. Los cambios de la composición vegetal debidos al pastoreo y la fertilización, principalmente incrementos de la dominancia, se relacionaron con aumentos de la biomasa aérea. Por último, el pastoreo y la diversidad de especies y grupos funcionales de plantas promovieron la estabilidad de la PPNA, mientras que los niveles intermedios de dominancia de especies la disminuyeron. Esta tesis avanzó en el conocimiento de los mecanismos que regulan la interacción entre el pastoreo doméstico y los aumentos crónicos de nutrientes sobre la estructura, funcionamiento y estabilidad de la vegetación, lo que va a permitir mejorar las estrategias de manejo y conservación de los pastizales templados

Livestock exclusion reduces the temporal stability of grassland productivity regardless of eutrophication

Changes in livestock loads and eutrophication associated with human activities can modify the stability of grassland's aboveground net primary productivity (ANPP), by modifying the mean (μ) and/or standard deviation (σ) of ANPP. The changes in attributes of the plant community (i.e., species richness, species asynchrony, dominance) might in turn explain the ecosystem temporal (inter-annual) stability of grassland production. Here, we evaluated the interactive effects of changes in livestock loads and chronic nutrient addition on the temporal stability of ANPP (estimated as μ/σ) in temperate grasslands. We also assessed the role of different attributes of the plant community on ecosystem stability. We carried out a factorial experiment of domestic livestock exclusion and nutrient addition (10 g.m−2.year−1 of nitrogen, phosphorus, and potassium; n = 6 blocks) during five consecutive years in a natural grassland devoted to cattle production (Flooding Pampa, Argentina). Domestic livestock exclusion reduced ANPP stability by 65%, regardless of nutrient load, mainly by the increase of ANPP standard deviation. This reduction in ANPP stability after livestock exclusion was associated mostly with higher plant species dominance and also with reductions in plant effective richness and in the asynchrony of grassland's species. Despite not finding direct negative effects of eutrophication on ANPP stability, chronic nutrient addition decreased effective species richness and asynchrony, which may translate into reductions in ANPP stability in the future. Our findings highlight that the presence of livestock maintains the temporal stability of ANPP mainly by lowering the dominance of the plant community. However, increases in nutrient loads in grasslands devoted to livestock production may threaten grassland's stability.Fil: Campana, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente; ArgentinaFil: Tognetti, Pedro Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; ArgentinaFil: Yahdjian, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente; Argentin

Arid community responses to nitrogen and carbon addition depend on dominant species traits and are decoupled between above- and below-ground biomass

Questions: Arid communities are strongly limited by soil resources including water and nitrogen (N). Plants compete for N with other plants and microorganisms, which are also limited by carbon (C). We propose that above- and below-ground plant responses to soil resources are modulated by community structure (species relative abundances, “mass ratio hypothesis”) and species traits (relative growth rates — RGRs). We evaluated the single and combined effects of soil N and C addition on the above- and below-ground biomass accumulation of perennial grass patches in an arid community, and the mechanisms involved in their responses. Location: Patagonian steppe, Argentina. Methods: We added N (2 g N m−2; NH4NO3) and C (330 g C m−2; sucrose) to 1-m2 field plots in a factorial design. After two years, we harvested above-ground (n = 5 plots) and below-ground biomass (n = 10 soil cores) and sorted it by species. We measured potential soil respiration as a proxy of microbial activity. Results: Total above-ground biomass increased by 55% as a result of N and decreased by 45% as a result of C addition, in relation to controls. C addition reduced total below-ground biomass by 42%. The above-ground differences were associated with changes in the biomass of dominant species according to their RGRs. Poa ligularis (dominant, high RGR) increased by 92% as a result of N addition while Pappostipa speciosa (dominant, low RGR) decreased by 55% as a result of C addition. Intermediate and subordinate grasses did not modify their biomass, independently of their RGR. Potential soil respiration was three times higher in plots with C addition than in control plots. Conclusions: Community biomass was explained by a combination of mass ratio hypothesis and specific RGR, as dominant grasses controlled above-ground community responses to N (high-RGR species) and C addition (low-RGR species). Our findings highlight the independence between the above- and below-ground processes and the importance of considering community equitability and species characteristics to predict plant community responses to changes in soil resources.Fil: Campana, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Reyes, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Aguiar, Martin Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

TWEAK/Fn14 signalling promotes cholangiocarcinoma niche formation and progression.

Background & Aims: Cholangiocarcinoma (CCA) is a cancer of the hepatic bile ducts that is rarely resectable and is associated with poor prognosis. Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is known to signal via its receptor fibroblast growth factor-inducible 14 (Fn14) and induce cholangiocyte and myofibroblast proliferation in liver injury. We aimed to characterise its role in CCA. Methods: The expression of the TWEAK ligand and Fn14 receptor was assessed immunohistochemically and by bulk RNA and single cell transcriptomics of human liver tissue. Spatiotemporal dynamics of pathway regulation were comprehensively analysed in rat and mouse models of thioacetamide (TAA)-mediated CCA. Flow cytometry, qPCR and proteomic analyses of CCA cell lines and conditioned medium experiments with primary macrophages were performed to evaluate the downstream functions of TWEAK/Fn14. In vivo pathway manipulation was assessed via TWEAK overexpression in NICD/AKT-induced CCA or genetic Fn14 knockout during TAA-mediated carcinogenesis. Results: Our data reveal TWEAK and Fn14 overexpression in multiple human CCA cohorts, and Fn14 upregulation in early TAA-induced carcinogenesis. TWEAK regulated the secretion of factors from CC-SW-1 and SNU-1079 CCA cells, inducing polarisation of proinflammatory CD206+ macrophages. Pharmacological blocking of the TWEAK downstream target chemokine monocyte chemoattractant protein 1 (MCP-1 or CCL2) significantly reduced CCA xenograft growth, while TWEAK overexpression drove cancer-associated fibroblast proliferation and collagen deposition in the tumour niche. Genetic Fn14 ablation significantly reduced inflammatory, fibrogenic and ductular responses during carcinogenic TAA-mediated injury. Conclusion: These novel data provide evidence for the action of TWEAK/Fn14 on macrophage recruitment and phenotype, and cancer-associated fibroblast proliferation in CCA. Targeting TWEAK/Fn14 and its downstream signals may provide a means to inhibit CCA niche development and tumour growth. Lay summary: Cholangiocarcinoma is an aggressive, chemotherapy-resistant liver cancer. Interactions between tumour cells and cells that form a supportive environment for the tumour to grow are a source of this aggressiveness and resistance to chemotherapy. Herein, we describe interactions between tumour cells and their supportive environment via a chemical messenger, TWEAK and its receptor Fn14. TWEAK/Fn14 alters the recruitment and type of immune cells in tumours, increases the growth of cancer-associated fibroblasts in the tumour environment, and is a potential target to reduce tumour formation

Senolytic treatment preserves biliary regenerative capacity lost through cellular senescence during cold storage

Liver transplantation is the only curative option for patients with end-stage liver disease. Despite improvements in surgical techniques, nonanastomotic strictures (characterized by the progressive loss of biliary tract architecture) continue to occur after liver transplantation, negatively affecting liver function and frequently leading to graft loss and retransplantation. To study the biological effects of organ preservation before liver transplantation, we generated murine models that recapitulate liver procurement and static cold storage. In these models, we explored the response of cholangiocytes and hepatocytes to cold storage, focusing on responses that affect liver regeneration, including DNA damage, apoptosis, and cellular senescence. We show that biliary senescence was induced during organ retrieval and exacerbated during static cold storage, resulting in impaired biliary regeneration. We identified decoy receptor 2 (DCR2)–dependent responses in cholangiocytes and hepatocytes, which differentially affected the outcome of those populations during cold storage. Moreover, CRISPR-mediated DCR2 knockdown in vitro increased cholangiocyte proliferation and decreased cellular senescence but had the opposite effect in hepatocytes. Using the p21KO model to inhibit senescence onset, we showed that biliary tract architecture was better preserved during cold storage. Similar results were achieved by administering senolytic ABT737 to mice before procurement. Last, we perfused senolytics into discarded human donor livers and showed that biliary architecture and regenerative capacities were better preserved. Our results indicate that cholangiocytes are susceptible to senescence and identify the use of senolytics and the combination of senotherapies and machine-perfusion preservation to prevent this phenotype and reduce the incidence of biliary injury after transplantation.This work was supported by the UK Medical Research MRC (MR/K017047/1) (to S.J.F.), the Computational and Chemical Biology of Stem Cell Niche (MR/L012766/1) (to S.J.F.), the UK Regenerative Medicine Platform (MR/K026666/1) (to S.J.F.), and the Wellcome Trust Institutional Translational Partnership Award (WT iTPA) (to S.F.-G.). J.M.B. was supported by the Spanish Carlos III Health Institute (ISCIII) (PI15/01132, PI18/01075, and Miguel Servet Program CON14/00129 and CPII19/00008) cofinanced by “Fondo Europeo de Desarrollo Regional” (FEDER); “Instituto de Salud Carlos III” (CIBERehd), Spain; “Euskadi RIS3” (2019222054 and 2020333010); and the Department of Industry of the Basque Country (Elkartek: KK-2020/00008). This research was funded in whole or in part by The Wellcome Trust (grant number 209710/Z/17/Z), a cOAlition S organization

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Plant quality and primary productivity modulate plant biomass responses to the joint effects of grazing and fertilization in a mesic grassland

Questions: Human activities are increasing the density of domestic grazers and global nutrient loads, modifying the main determinants of vegetation community dynamics. Grazing (top-down control) and nutrient availability (bottom-up control) may interactively modify plant biomass, which is particularly important in grasslands devoted to livestock production. Here, we aim to understand the interactive effects of grazing and fertilization on grassland plant biomass. We hypothesized that the joint effects of nutrient addition and domestic grazing on above-ground plant biomass are not additive, but they modify each other through changes in ground-level light, leaf nutritional quality, above-ground net primary productivity (ANPP), and below-ground plant allocation. Location: Flooding Pampa (Buenos Aires, Argentina). Methods: We carried out a factorial experiment of grazing exclusion and fertilization with nitrogen, phosphorus, and potassium + micronutrients during ​several years in a mesic grassland devoted to livestock production. Results: After four years, grazing reduced live above-ground plant biomass by 52%, and when combined with fertilization this reduction was 70%. Nutrient addition in the grazed grassland increased ANPP and leaf nutrient concentration. These changes in turn intensified grazing pressure and cattle’s plant consumption. By contrast, fertilization did not produce any significant effect on plant biomass or ANPP inside the exclosures, where ground-level light was low. A structural equation model revealed that the increase in ANPP fostered above-ground and reduced below-ground plant biomass. Conclusions: This is the first study conducted in the Pampas grasslands that evaluated the effect of cattle grazing and fertilization on plant communities under field conditions over several years. Grazing and nutrient addition synergistically controlled grassland plant biomass, as the reduction in above-ground biomass by cattle consumption was greater in fertilized plots. Our results provided empirical evidence that leaf nitrogen and ANPP modulated plant biomass dynamics in grasslands devoted to livestock production in the context of increased nutrient loads in terrestrial ecosystems.Fil: Campana, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Yahdjian, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

Plan de marketing para el diario Norte Express - Empresa Editora El Comercio

Este trabajo de investigación desarrolla un plan de marketing para la Empresa Editora El Comercio donde se plantea un modelo de negocio pensado en ofrecer un medio de información impreso gratuito y localizado. Este medio está orientado a hombres y mujeres de niveles socioeconómicos B y C que vivan, estudien y/o trabajen en Lima Norte, específicamente en los distritos de Comas, Independencia, Los Olivos y San Martín